Added support for Translatable

Adds solr support for translatable (uses multiple cores).
Set the locale for each solr index (which extend SolrIndex) in config yml:

ChineseSiteSearchIndex:
  limitToLocale: zh_CN
SiteSearchIndex:
  limitToLocale: en_NZ

It will then append the correct locale to the cmd.

I also added the ability to quickly run a simple reindex on a particular index:
sake dev/tasks/Solr_Reindex index=ChineseSiteSearchIndex verbose=1